Safety switch



Patented May 27, 1.952

UNITED STATES PATENT OFFICE SAFETY SWITCH Hugh M. Barton, Fort Worth,Tex.

Application May 19, 1948, Serial No. 27,910

(Cl. 20D-44) 2 Claims. 1

This invention relates to safety switches for electrical circuits foroperating machinery, such as lathes and similar machines, and it hasparticular reference to an enclosed switch capable of operation to beopened or closed only by a lathe wrench or chuck key, or other tool usedon the machine in whose circuit the switch is installed, and itsprincipal object resides in the provision of a compact housing in whicha conventional electrical service switch can be installed and which isaccessible only through an opening suited to the reception of a lathechuck key, or a similar instrument, by which the switch can be operatedto open or close the circuit.

A prime object of the invention is that of providing a safety switch bywhich a lathe, for example, cannot be operated without employing a chuckwrench or key to actuate the switch and which must remain in the switchhousing as long as the circuit is closed and be incapable of withedrawal therefrom until the switch is turned to open the circuit to stopthe machine, the chuck wrench or key not being usable on the machine aslong as the circuit is closed and the machine is in operation.

Another object of the invention resides in the provision of a simple andinexpensive structure capable of being economically installed in anymachine circuit and arranged upon or near the machine in easy access tothe operator so that a wrench or key employed on the machine can be usedon the latter when the same is not in operation, yet must be utilized asa means for actuating the switch to cause the machine to function, thuspreventing injury and damage to the operator and property by theinadvertence or carelessness of the operator in leaving the chuck wrenchor key on the machine while it is in motion.

Broadly, the invention contemplates the provision of a safety devicewhich is calculated to reduce accidents to machinists and machineoperators due to thoughtlessness in leaving detachable tools secured tothe lathe after the usual operative adjustments have been completed,making it necessary to remove the wrench from the lathe before thelatter can be put in motion.

While the foregoing objects are paramount, other and lesser objects willbecome manifest as the description proceeds, taken in connection withthe appended drawings wherein:

Figure 1 is a vertical cross-sectional illustration of the invention,taken on lines I-I of Figure 2, illustrating a conventional toggle-typeof switch arranged within the housing, the switch actuating plate, andthe key locking devices.

Figure 2 is a vertical cross-sectional view, taken on lines 2 2 ofFigure 1, showing the front cover removed, the rotatableswitch-actuating member, and the key locking devices, their lockedposition being indicated in dotted lines.

Figure 3 is a vertical cross-sectional view, similar to that shown inFigure 1, illustrating the key in position and the locking devicesretaining the same, and

Figure 1i is a rear internal view of the housing showing the back coverremoved and illustrating the operative positions of the switch,partially in dotted lines.

Accordingly, therefore, the invention comprises a housing l), preferablycircular in form, and having one integral wall I I providing the face orthe front cover of the housing l0. It is preferable to form the housingwith an integral annular fiange i2 concentrically of the housing I0, asillustrated in Figures 1 and 2, which projects toward the rear of thehousing providing a circular chamber I3 in which are arranged theoperative parts of the switch-operating mechanism.

A disk I d, having a diameter adapting the same to a relatively closefit within the chamber I3, is secured in position therein by a ring I5attached by screws l5 to the annular flange I2. The disk i4 is formedwith an annular recess I1 about its rearmost side providing a seat forthe ring I5, the rear surface of the disk I4 being flush with the ringI5, as apparent in Figures 1 and 3.

A conical milled opening I8 is formed in the disk i4, as shown inFigures 1 and 2, whose teeth I9 are conformable to the teeth 20 on thechuck wrench or key 2l which is employed to rotate the disk I4 to openor close the switch 22 secured by a suitable bracket 23 to the ring I5.The switch 22 has a toggle-type of operating lever 24 which depends, asin Figures 1, 3 and 4, and is capable of being moved to open or closethe position of the poles by rearwardly projecting pins 25 arranged oneach side of the depending lever 2li and secured in the rear surface ofthe disk member i4.

Attached to the outer face of the disk I4 is a pair of opposinglyarranged detents 26, one on each side of the opening I8, as in Figure 2,which are slidably secured by screws 21 to the face of the member iiiand normally retained in retracted position by springs 28 arrangedwithin bores 29 in each of the members 25, as shown in Figures 1 and 2,and bearing against the outer end of the bores 29 at one end, andagainst blocks 30 arranged about the screws 21 at the opposite end.

In operation, therefore, the circuit is closed to operate the lathe, orother machine to which the safety switch is attached, by inserting thewrench or key 2l through an opening 3l in the front Ii of the housing I,as illustrated in Figure 3, so that the toothed bur 32 on the key 2|engages the conical milled opening I8, the teeth I!) and 26 meshing,whereupon the disk member I4 can be rotated clockwise within the chamberi3, whose inner wall defines a pair of opposing cams against which theouter ends 34 of the members 26 normally bear, as in Figure 2, urgingthe members 25 inwardly, as illustrated in dotted lines in Figure 2, topositions behind the bur 32 of the wrench 2l, locking the latter inposition so that it cannot be removed until it is rotatedcounterclockwise to the position illustrated in Figure 2 whichautomatically opens the switch 22 through the medium of the pins 25, asillustrated in Figure 4. The machine operator may then remove the wrenchor key 2| and perform whatever adjustments he may require on themachine, but before the machine can be again placed in motion, the key2l must be returned to the position shown in Figure 3, the key havingbeen rotated clockwise to the position shown in dotted lines in Figure2.

The switch 22 is preferably arranged in the upper portion of the housingl!) so that the service lines 35 can be connected thereto upon enteringthe housing l through a suitable opening 36 in its top, as in Figures 1and 3.

Maniiestly, the structure herein shown and described is capable ofconsiderable modification from time to time, by persons skilled in theart, without departing from the spirit and intent of the invention orthe scope of the appended claims.

What is claimed is:

1. In a safety switch for lathes, andthe like,

in combination with a toggle switch in an electrical circuit and ahousing for said switch, a rotatable disk arranged in said housing andhaving a pair of pins projecting from the face thereof operativelyengageable with the lever of said toggle switch, means comprising amilled opening formed in said rotatable disk adapted to receive a milledkey for rotating same to actuate said toggle switch, tensioned latchmembers arranged on said rotatable member locking said key in positionwhen said circuit is closed, and cam means forming part of said housingactuating said latch members.

2. In a safety switch for machines, and the like, in combination with atoggle switch in an electrical circuit and a housing for said toggleswitch, a rotatable disk in said housing having a pair oi' pinsprojecting from the rear face thereof cooperating with said toggleswitch and capable of engaging the lever of said switch when rotated,means comprising a milled opening in said disk for receiving a key forrotating the same, tensioned locking members securing said key in saidkey receiving means when said circuit is closed, and cam means formingpart of said housing actuating said locking members when said key isrotated.

HUGH M. BARTON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,180,667 Martin Apr. 25, 19161,441,618 Winning Jan. 9, 1923 1,591,646 Schaefer July 6, 1926 1,785,906Koffer Dec. 23, 1930 1,885,147 Smith Nov. 1, 1932

